diffcore: add a pickaxe option to find a specific blob

Sometimes users are given a hash of an object and they want to
identify it further (ex.: Use verify-pack to find the largest blobs,
but what are these? or [1])

One might be tempted to extend git-describe to also work with blobs,
such that `git describe <blob-id>` gives a description as
'<commit-ish>:<path>'.  This was implemented at [2]; as seen by the sheer
number of responses (>110), it turns out this is tricky to get right.
The hard part to get right is picking the correct 'commit-ish' as that
could be the commit that (re-)introduced the blob or the blob that
removed the blob; the blob could exist in different branches.

Junio hinted at a different approach of solving this problem, which this
patch implements. Teach the diff machinery another flag for restricting
the information to what is shown. For example:

    $ ./git log --oneline --find-object=v2.0.0:Makefile
    b2feb64309 Revert the whole "ask curl-config" topic for now
    47fbfded53 i18n: only extract comments marked with "TRANSLATORS:"

we observe that the Makefile as shipped with 2.0 was appeared in
v1.9.2-471-g47fbfded53 and in v2.0.0-rc1-5-gb2feb6430b.  The
reason why these commits both occur prior to v2.0.0 are evil
merges that are not found using this new mechanism.

[1] https://stackoverflow.com/questions/223678/which-commit-has-this-blob
[2] https://public-inbox.org/git/20171028004419.10139-1-sbeller@google.com/

Signed-off-by: Stefan Beller <sbeller@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
pull/409/merge
Stefan Beller 5 years ago committed by Junio C Hamano
parent cf63051ada
commit 15af58c1ad
  1. 10
      Documentation/diff-options.txt
  2. 21
      diff.c
  3. 8
      diff.h
  4. 45
      diffcore-pickaxe.c
  5. 3
      revision.c
  6. 68
      t/t4064-diff-oidfind.sh

@ -492,6 +492,15 @@ occurrences of that string did not change).
See the 'pickaxe' entry in linkgit:gitdiffcore[7] for more
information.
--find-object=<object-id>::
Look for differences that change the number of occurrences of
the specified object. Similar to `-S`, just the argument is different
in that it doesn't search for a specific string but for a specific
object id.
+
The object can be a blob or a submodule commit. It implies the `-t` option in
`git-log` to also find trees.
--pickaxe-all::
When `-S` or `-G` finds a change, show all the changes in that
changeset, not just the files that contain the change
@ -500,6 +509,7 @@ information.
--pickaxe-regex::
Treat the <string> given to `-S` as an extended POSIX regular
expression to match.
endif::git-format-patch[]
-O<orderfile>::

@ -4082,6 +4082,7 @@ void diff_setup(struct diff_options *options)
options->interhunkcontext = diff_interhunk_context_default;
options->ws_error_highlight = ws_error_highlight_default;
options->flags.rename_empty = 1;
options->objfind = NULL;
/* pathchange left =NULL by default */
options->change = diff_change;
@ -4487,6 +4488,23 @@ static int parse_ws_error_highlight_opt(struct diff_options *opt, const char *ar
return 1;
}
static int parse_objfind_opt(struct diff_options *opt, const char *arg)
{
struct object_id oid;
if (get_oid(arg, &oid))
return error("unable to resolve '%s'", arg);
if (!opt->objfind)
opt->objfind = xcalloc(1, sizeof(*opt->objfind));
opt->pickaxe_opts |= DIFF_PICKAXE_KIND_OBJFIND;
opt->flags.recursive = 1;
opt->flags.tree_in_recursive = 1;
oidset_insert(opt->objfind, &oid);
return 1;
}
int diff_opt_parse(struct diff_options *options,
const char **av, int ac, const char *prefix)
{
@ -4736,7 +4754,8 @@ int diff_opt_parse(struct diff_options *options,
else if ((argcount = short_opt('O', av, &optarg))) {
options->orderfile = prefix_filename(prefix, optarg);
return argcount;
}
} else if (skip_prefix(arg, "--find-object=", &arg))
return parse_objfind_opt(options, arg);
else if ((argcount = parse_long_opt("diff-filter", av, &optarg))) {
int offending = parse_diff_filter_opt(optarg, options);
if (offending)

@ -7,6 +7,7 @@
#include "tree-walk.h"
#include "pathspec.h"
#include "object.h"
#include "oidset.h"
struct rev_info;
struct diff_options;
@ -173,6 +174,8 @@ struct diff_options {
enum diff_words_type word_diff;
enum diff_submodule_format submodule_format;
struct oidset *objfind;
/* this is set by diffcore for DIFF_FORMAT_PATCH */
int found_changes;
@ -325,8 +328,11 @@ extern void diff_setup_done(struct diff_options *);
#define DIFF_PICKAXE_KIND_S 4 /* traditional plumbing counter */
#define DIFF_PICKAXE_KIND_G 8 /* grep in the patch */
#define DIFF_PICKAXE_KIND_OBJFIND 16 /* specific object IDs */
#define DIFF_PICKAXE_KINDS_MASK (DIFF_PICKAXE_KIND_S | DIFF_PICKAXE_KIND_G)
#define DIFF_PICKAXE_KINDS_MASK (DIFF_PICKAXE_KIND_S | \
DIFF_PICKAXE_KIND_G | \
DIFF_PICKAXE_KIND_OBJFIND)
#define DIFF_PICKAXE_IGNORE_CASE 32

@ -124,13 +124,20 @@ static int pickaxe_match(struct diff_filepair *p, struct diff_options *o,
mmfile_t mf1, mf2;
int ret;
if (!o->pickaxe[0])
return 0;
/* ignore unmerged */
if (!DIFF_FILE_VALID(p->one) && !DIFF_FILE_VALID(p->two))
return 0;
if (o->objfind) {
return (DIFF_FILE_VALID(p->one) &&
oidset_contains(o->objfind, &p->one->oid)) ||
(DIFF_FILE_VALID(p->two) &&
oidset_contains(o->objfind, &p->two->oid));
}
if (!o->pickaxe[0])
return 0;
if (o->flags.allow_textconv) {
textconv_one = get_textconv(p->one);
textconv_two = get_textconv(p->two);
@ -226,20 +233,22 @@ void diffcore_pickaxe(struct diff_options *o)
cflags |= REG_ICASE;
regcomp_or_die(&regex, needle, cflags);
regexp = &regex;
} else if (o->pickaxe_opts & DIFF_PICKAXE_IGNORE_CASE &&
has_non_ascii(needle)) {
struct strbuf sb = STRBUF_INIT;
int cflags = REG_NEWLINE | REG_ICASE;
basic_regex_quote_buf(&sb, needle);
regcomp_or_die(&regex, sb.buf, cflags);
strbuf_release(&sb);
regexp = &regex;
} else {
kws = kwsalloc(o->pickaxe_opts & DIFF_PICKAXE_IGNORE_CASE
? tolower_trans_tbl : NULL);
kwsincr(kws, needle, strlen(needle));
kwsprep(kws);
} else if (opts & DIFF_PICKAXE_KIND_S) {
if (o->pickaxe_opts & DIFF_PICKAXE_IGNORE_CASE &&
has_non_ascii(needle)) {
struct strbuf sb = STRBUF_INIT;
int cflags = REG_NEWLINE | REG_ICASE;
basic_regex_quote_buf(&sb, needle);
regcomp_or_die(&regex, sb.buf, cflags);
strbuf_release(&sb);
regexp = &regex;
} else {
kws = kwsalloc(o->pickaxe_opts & DIFF_PICKAXE_IGNORE_CASE
? tolower_trans_tbl : NULL);
kwsincr(kws, needle, strlen(needle));
kwsprep(kws);
}
}
/* Might want to warn when both S and G are on; I don't care... */
@ -248,7 +257,7 @@ void diffcore_pickaxe(struct diff_options *o)
if (regexp)
regfree(regexp);
else
if (kws)
kwsfree(kws);
return;
}

@ -2412,6 +2412,9 @@ int setup_revisions(int argc, const char **argv, struct rev_info *revs, struct s
revs->diffopt.flags.follow_renames)
revs->diff = 1;
if (revs->diffopt.objfind)
revs->simplify_history = 0;
if (revs->topo_order)
revs->limited = 1;

@ -0,0 +1,68 @@
#!/bin/sh
test_description='test finding specific blobs in the revision walking'
. ./test-lib.sh
test_expect_success 'setup ' '
git commit --allow-empty -m "empty initial commit" &&
echo "Hello, world!" >greeting &&
git add greeting &&
git commit -m "add the greeting blob" && # borrowed from Git from the Bottom Up
git tag -m "the blob" greeting $(git rev-parse HEAD:greeting) &&
echo asdf >unrelated &&
git add unrelated &&
git commit -m "unrelated history" &&
git revert HEAD^ &&
git commit --allow-empty -m "another unrelated commit"
'
test_expect_success 'find the greeting blob' '
cat >expect <<-EOF &&
Revert "add the greeting blob"
add the greeting blob
EOF
git log --format=%s --find-object=greeting^{blob} >actual &&
test_cmp expect actual
'
test_expect_success 'setup a tree' '
mkdir a &&
echo asdf >a/file &&
git add a/file &&
git commit -m "add a file in a subdirectory"
'
test_expect_success 'find a tree' '
cat >expect <<-EOF &&
add a file in a subdirectory
EOF
git log --format=%s -t --find-object=HEAD:a >actual &&
test_cmp expect actual
'
test_expect_success 'setup a submodule' '
test_create_repo sub &&
test_commit -C sub sub &&
git submodule add ./sub sub &&
git commit -a -m "add sub"
'
test_expect_success 'find a submodule' '
cat >expect <<-EOF &&
add sub
EOF
git log --format=%s --find-object=HEAD:sub >actual &&
test_cmp expect actual
'
test_done
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